1. Field of the Invention
This invention relates to the art of printing bands and to method of making printing bands.
2. Brief Description of the Prior Art
The following prior art U.S. patents are made of record: U.S. Pat. Nos. 685,473; 798,460; 2,950,048; 3,418,929; 3,968,745; 3,977,321; 4,263,242; and 4,392,424.
Some prior art printing bands have a column of raised outwardly projecting printing characters and a column of raised outwardly projecting visually readable characters. Because the column of printing characters occupies almost one half of the band length, the printing characters are considered to comprise the printing-half of the band, and likewise because the column of visually readable character occupies almost one-half of the band length, the visually readable characters are considered to comprise the read-half of the band. In that both the printing characters and the visually readable characters are raised, both the part of the mold which forms the printing-half and the part of the mold that forms the read-half are made from engraved dies. In that both the printing characters and the read characters are raised, the print cavity portions for forming the printing characters and the read cavity portions for forming the read characters are provided by recesses in the dies. The manufacture of dies with small print cavity portions is difficult, and the manufacture of dies with even smaller print cavity portions is even more difficult because the engraving tool is required to engrave contours inside a cavity. It sometimes happens that a small air bubble will prevent the moldable elastomeric material from filling the cavity portions. This is due to the fact that the ends of individual print cavity portions and read cavity portions are not vented. This bubble can cause a void in a printing character or in a visually readable character. A void in a printing character can cause that printing character to print poorly, and a void in a visually readable character can cause the visually readable character to be more difficult to read. It sometimes happens that part of a printing character or part of a visually readable character becomes stuck in a respective printing cavity portion or in a visually readable cavity portion. Consequently, when the band is removed from the mold, part of the printing character and/or part of the visually readable character is torn off and remains in the mold. This degrades the quality of the band and means that the band has to be scrapped. Also, when elastomeric material is struck in a cavity portion, unless removed, that material can form a void in subsequent printing bands that are molded.
The elastomeric material from which the bands are molded is typically black or dark in color. It is very difficult to read the visually readable characters unless there is some contrasting color. A technique for rendering raised visually readable characters more readily readable is found in co-owned U.S. Pat. No. 4,263,242. Another is found in co-owned pending U.S. patent application Ser. No. 09/238,986 filed Jan. 28, 1999. Yet another known technique is to simply coat the tops of the visually readable characters with a coating of a color-contrasting material. Such further processing of the printing band adds cost to the manufacturing process. A flaw in any added step in the process may result in a scrap printing band, thereby raising the cost of useable printing bands.